The invention relates to a laser amplification system comprising several solid-state volumes having a laser-active medium, a pumping radiation source for generating a pumping radiation field for the optical pumping of the laser-active medium, a pumping radiation reflector which is associated with each solid-state volume and allows a leg of the pumping radiation field entering the solid-state volume to pass through the solid-state volume again as an outgoing leg such that the incoming leg and the outgoing leg form an angle with one another located in a plane and thereby form a first pumping branch, a first pumping radiation path through the solid-state volumes, in which the first pumping branches are arranged so as to follow one another such that the pumping radiation field passes through the several solid-state volumes in a first sequence.
Laser amplification systems of this type are known, for example, from EP 0 632 551.
In the case of laser amplification systems with solid-state volumes having a laser-active medium the problem exists that a pumping light excitation of the individual solid-state bodies is brought about with varying pumping power.
The object underlying the invention is therefore to provide a laser amplification system with several solid-state volumes, with which the individual solid-state volumes are acted upon with pumping power as uniformly as possible.
This object is accomplished in accordance with the invention, in a laser amplification system of the type described at the outset, in that each solid-state volume is penetrated by a second pumping branch, the incoming leg of which and the outgoing leg of which are located in a second plane different to the first plane and in this form an angle with one another, that a second pumping radiation path is provided, in which the second pumping branches of the several solid-state volumes are arranged so as to follow one another such that the pumping radiation field passes through the solid-state volumes in a second sequence.
The advantage of the inventive solution is to be seen in the fact that with the second pumping radiation path the possibility is created of pumping each of the solid-state volumes with the same number of pumping branches and, in addition, of introducing the pumping power in the solid-state volumes to be pumped as uniformly as possible on account of the fact that the two pumping branches are located in different planes.
This has the advantage, in particular, with a view to the type of thin, disk-shaped solid-state bodies, which are provided in the inventive solution and are preferably located with a flat side on a cooling surface, that, as a result, the design of as uniform a temperature curve as possible with planes of essentially the same temperature extending parallel to the flat sides of the solid-state bodies is facilitated which is essential for the advantageous working within the scope of the inventive concept.
It is particularly favorable when in the second sequence the order of the solid-state bodies is changed in relation to the first sequence. This solution allows the reduction in intensity in the sequence to be counteracted as a result of the changed order.
With respect to the type of supply to the first and second pumping radiation paths, no further details have so far been given. One advantageous embodiment, for example, provides for each of the pumping light radiation paths to be supplied by its own pumping radiation source, wherein it is preferably provided for the pumping radiation sources to have essentially the same power.
Another alternative embodiment provides for the pumping radiation paths to be supplied by a single pumping radiation source. This has the advantage thatxe2x80x94insofar as the radiation power of a single pumping radiation source is sufficientxe2x80x94this can be used for both pumping radiation paths.
In this respect, there are different possibilities for realizing the supply to the two pumping radiation paths with one pumping radiation source.
One possibility is for the pumping radiation field from the pumping radiation source to be divided between the two pumping radiation paths by a beam divider.
This solution has the advantage that, as a result, the possibility exists of supplying both pumping radiation paths with pumping radiation fields of essentially the same intensity.
Another advantageous solution provides for the pumping radiation paths to be coupled to one another by an optical deflection means, i.e. for the pumping radiation field to be coupled in by an optical deflection means with the intensity which is present at the end of one of the pumping radiation paths such that this supplies the next pumping radiation path. This solution is particularly expedient when the intensity absorbed per pumping radiation path is not very large and so following the first pumping radiation path a power of the pumping radiation field is nevertheless available which is sufficiently large to supply the second pumping radiation path.
In principle, it is provided within the scope of the inventive solution for the pumping radiation field to pass through each pumping radiation path in one direction. To improve the pumping of the solid-state bodies it is, however, also advantageous when the pumping radiation field passes through each pumping radiation path in two opposite direction. This is irrespective of whether two pumping radiation sources are provided for supplying the pumping radiation paths or only one pumping radiation source, the power of which can be coupled into the pumping radiation paths in the different ways already described.
A solution, which is particularly simple to realize and with which the pumping radiation field passes through each pumping radiation path twice, provides for a reflector to be arranged at one end of each pumping radiation path and for this to reflect back the pumping radiation field exiting from the pumping radiation path.
In conjunction with the preceding solutions it has merely been specified that the order of the solid-state volumes in the second sequence is intended to be different to that in the first sequence. This may be realized in the most varied of ways, in particular, in a different manner when not only a first sequence and a second sequence are provided but rather several sequences exceeding the first and the second sequences. In the simplest case of a first and a second sequence it is, however, preferably provided for the order of the solid-state volumes in the second sequence to be reversed in relation to the first sequence.
So far, it has been specified in conjunction with the inventive solution that there is a first pumping radiation path and a second pumping radiation path. The inventive solution is, however, not limited to two pumping radiation paths with first and second pumping branches, respectively. On the contrary, it is possible in a further inventive solution for at least one additional pumping radiation path to be provided, with which the pumping radiation field passes through the solid-state bodies in the form of at least one additional sequence. The advantage of this solution is to be seen in the fact that with it an even more uniform excitation of the solid-state bodies can be realized.
This may be realized particularly favorably when the at least one additional sequence runs such that this counteracts varying pumping excitations of the laser-active material in the solid-state volume as a result of the first and the second sequences.
It is, in particular, advantageous when the number of pumping radiation paths is an even number so that the fact that with each pumping radiation path the pumping radiation field pumps from the one pumping branch to the other pumping branch with lower power can be compensated particularly favorably.
With respect to the manner, in which the individual pumping branches of one pumping radiation path are coupled, no particular details have been given. One advantageous embodiment, for example, provides for the individual pumping branches of a pumping radiation path to be coupled by optical refocusing means.
These optical refocusing means may be designed in the most varied of ways. One type of design provides, for example, for the optical refocusing means to image the outgoing leg of a pumping branch directly into the corresponding incoming leg of the next pumping branch.
The advantage of this solution lies in its simplicity. These solutions do, however, have the problem that either the pumping light radiation spot is increased in size or a cross section of the pumping radiation field becomes ever larger from optical refocusing means to optical refocusing means.
For this reason, one inventive solution which is improved in this respect provides for at least one of the optical refocusing means to be designed as an intermediately collimating optical refocusing means and to image the respective outgoing leg via an intermediately collimated leg into the corresponding incoming leg. This solution has the advantage that as a result of the intermediate collimation it is possible to avoid any increase in the size of the cross section of the pumping radiation field.
In this respect, the intermediately collimated legs are preferably designed such that their imaging corresponds to the imaging which is obtained with the sum of the focal distances of the optical means provided on both sides of the intermediately collimated leg. In the case of optical means having the same focal distance on both sides of the intermediately collimated leg, the imaging of the intermediately collimated leg corresponds to one with a double focal distance.
In this respect, it is particularly favorable when all the optical refocusing means are designed as intermediately collimating optical refocusing means so that during the entire course of the respective pumping radiation path no appreciable increase in the size of the cross section of the pumping radiation field is brought about and thus the necessity also does not exist of not imaging part of the radiation field or adapting the optical refocusing means to the increasing size of the cross section of the pumping radiation fields.
One particularly advantageous realization of an intermediately collimating optical refocusing means provides for this to have a folded collimated leg. Such a folded collimated leg creates, in particular, the possibility of designing the optical refocusing means to be space-saving.
Furthermore, a folding of the collimated leg creates the possibility of arranging the legs entering the respective solid-state bodies such that these always enter the solid-state volumes from the same side thereof.
With respect to the design of the intermediately collimating optical refocusing means, no particular details have so far been given. It is, for example, favorable for generating a folded collimated leg when the intermediately collimating optical refocusing means have a deflection element for the folding of the intermediately collimated leg.
To save on components in the case of the intermediately collimating optical refocusing means which require many components, it is preferably provided for one of the intermediately collimating optical refocusing means of the first and one of the intermediately collimating optical refocusing means of the second pumping radiation path to each image the respective, intermediately collimated leg onto a common deflection element so that only one deflection element is required for every two optical refocusing means.
Furthermore, no further details have been given with respect to the design of the intermediately collimating optical refocusing means as a whole. It is, for example, favorably provided for the intermediately collimating optical refocusing means to have a collimating element which images the respectively outgoing leg into the intermediately collimated leg.
Furthermore, it is favorable when the intermediately collimating optical refocusing means have a focusing element which images the intermediately collimated leg into the respectively incoming leg.
With respect to the optical elements which are used in the optical refocusing means, no further details have so far been given.
With respect to the simplicity in construction and spatial requirements, it has proven to be particularly advantageous when the optical refocusing means comprise hollow mirrors, wherein the hollow mirrors serve, in particular, to reshape the outgoing legs of a pumping branch directly into the corresponding incoming legs of the next pumping branch or serve to act as collimating and focusing elements.
In order to obtain particularly good optical images, it is preferably provided for the hollow mirrors to be designed as non-spherical mirrors since with spherical mirrors a not inconsiderable distortion always occurs which deteriorates too greatly the quality of the optical imaging with multiple reshaping of the pumping radiation field.
One embodiment, in particular, in the case of hollow mirrors which reshape an outgoing leg of a pumping branch directly into an incoming leg of the next pumping branch provides for the hollow mirrors to be designed as elliptical mirrors; with the elliptical shape of the mirrors a good quality of the optical imaging can be achieved with adaptation of the shape.
Another alternative embodiment, in particular, one, with which the hollow mirror is intended to represent a collimating or focusing element, provides for the hollow mirror to be designed as a parabolic mirror since a parabolic mirror is always in a position to focus a collimated leg or, vice versa, to collimate a divergent leg.
Not only the use of elliptical mirrors but also the use of parabolic mirrors entails considerable costs since these mirrors are complicated to produce.
For this reason, one advantageous solution provides for the hollow mirrors to be designed as toric mirrors. Toric mirrors of this type can replace not only elliptical mirrors but also parabolic mirrors, wherein the quality of the optical imaging is still sufficiently good, in particular, in the case of long focal distances.
With respect to the arrangement of the solid-state volumes relative to one another, no further details have been given. In principle, the most varied of arrangements of the solid-state volumes relative to one another would be conceivable. The inventive concept may be realized constructionally in a particularly favorable manner when the solid-state volumes are arranged along a line, wherein the line can, in principle, be a curved or a straight line. The individual optical refocusing means may be arranged in a particularly space-saving manner when the solid-state volumes are arranged along a straight line.
Furthermore, it is preferably provided for all the reflection surfaces of the reflectors associated with the solid-state volumes to be located in a common plane. In this case, the first and second pumping branches of the pumping radiation field then extending through the solid-state volumes are located in planes which are at right angles to the common plane of the reflection surfaces of all the reflectors.
In this case, the refocusing elements may preferably be arranged on different sides of a surface extending at right angles to the reflection surfaces and through the line, wherein one pumping branch of the pumping radiation field preferably extends between a refocusing element located on one side of the surface to a refocusing element located on the other side of the surfaces.
With respect to the different planes, in which the first and second pumping branches are intended to be located, no further details have likewise been given so far. One advantageous embodiment, for example, provides for the planes, in which the first and second pumping branches are located, to intersect at an angle of less than or equal to 90xc2x0.
With respect to the arrangement of the solid-state volumes, no further details have been given in conjunction with the preceding explanations concerning the individual embodiments. It would, for example, be conceivable, in particular, with a spatially very small design of the inventive solution to provide all the solid-state volumes in one solid-state body. For reasons of the spatial design it is advantageous, in particular, in the case of great power and thus large solid-state volumes when the several solid-state volumes having laser-active medium are arranged in several solid-state bodies, wherein a plurality of solid-state volumes can still be provided in each solid-state body.
It is advantageous, in particular, when achieving great power when each solid-state volume having laser-active medium is arranged in its own solid-state body so that an optimum cooling is brought about in the respective solid-state body, in particular, in the case of great power.